Commandos Boarding Vessels? How The US Could Blockade Iran
The U.S. military says it has successfully blocked ships from travelling out of Iran after beginning a naval blockade on Monday involving more than 10,000 troops, a dozen warships and scores of aircraft.
President Donald Trump announced the blockade on Sunday after negotiating talks broke down between Washington and Tehran, aimed at ending the war.
While Iran has deterred most ships from passing through the Strait of Hormuz since March, Iranian tankers have been allowed to make the transit to deliver oil to countries like China.
The U.S. blockade is aimed at stopping these exports to put pressure on Iran’s failing economy.
The U.S. Central Command (CENTCOM) on Tuesday claimed success on the first day, saying no ships had made it past the blockade and six merchant vessels had complied with orders to turn around.
At first it appeared that the the Rich Starry, a Chinese chemical and crude oil carrier known for carrying Iranian oil, had successfully exited the Strait of Hormuz, but it was seen back in the Persian Gulf on Wednesday.
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US navy interdiction of Chinese tanker Rich Starry
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So how is the U.S. operating its blockade? And why is it so risky?
‘Ghost’ Ships Could Try And Run The Blockade
There are big challenges in enforcement, says Steve Prest, an associate fellow at UK defence think tank the Royal United Services Institute, and a retired commodore with the UK Royal Navy.
In analysis shared with Newsweek, Prest said that the U.S. Fifth Fleet, normally headquartered in Bahrain and responsible for U.S. military operations in the Middle East, would have a comprehensive intelligence picture of merchant shipping traffic in the area.
But the challenge would be in tracking ships which seek to disguise their movements when their Automatic Identification Systems (AIS) report different location and movements to reality, known as "spoofing."
For instance, AIS could show the vessel at anchor in the Northern Gulf when it had in fact gone to Kharg Island.
Equally problematic could be if a vessel enters a third-nation's port before trying to exit the Strait of Hormuz, raising the question of when does a prior port visit count as a visit to Iran. The U.S. military had said that it was only stopping vessels that came from Iranian ports or coastal waters.
There is also the chance that such blockade running could take place using ship-to-ship transfers in international waters without the vessel ever having been inside Iran's territorial waters, Prest said.
"All of this will need to be tracked, assessed and decided upon before any action is taken," said Prest.
Assets to do this range from cyber, satellites, drones and AI-supported intelligence analysis through to maritime patrol aircraft, crewed warships, naval helicopters and commandos.
Prest said the main surveillance activity will take place in the Persian Gulf itself, to track the activity of the ships which are there and on the Iranian Coast in the Gulf of Oman.
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Iran and Gulf State Ports
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Where Is The U.S. Intercepting Ships?
Prest believes that any interdiction of shipping is likely to be further out in the Gulf of Oman or Arabian Sea, past the Strait of Hormuz, so that the US Navy ships will be out of reach of Iran’s coastal missile and drone batteries.
But that is a huge stretch of ocean – roughly 250,000 square miles – which would tie up several warships to maintain the blockade.
Shipping data displaying the route of ships like the Chinese-owned Rich Starry show that while it made it through the Strait of Hormuz, it had to turn around near Iran’s Jask port in the Gulf of Oman later on Tuesday. It has since returned to the Persian Gulf.
A U.S. Navy destroyer also stopped two oil tankers attempting to leave the Iranian port of Chabahar on Tuesday and instructed them to turn around, Reuters reported on Wednesday. Chabahar is Iran’s last port before ships leave the Gulf.
Could Commandos Board Vessels?
CENTCOM said guided-missile destroyers were among the assets executing the blockade. Each has a crew of more than 300 sailors "that are highly trained in conducting offensive and defensive maritime operations."
Prest said one or more ships would be needed to interdict a vessel and much would depend on the kind of ship being targeted.
"It may be that a boarding team is to be embarked onto the target ship," said Prest, "normally this would be led by commandos who would fast-rope down from a helicopter or climb a ladder from a boat."
It is highly unlikely that such boardings would be opposed by a civilian crew, but if the flag nations of the vessels, such as, say, China, decided to escort their tankers out of the area with warships of their own, or embark military detachments onboard the merchant vessel, "then the problem becomes far more complex," said Prest.
"It is highly unlikely the U.S. Navy would attempt to board vessels with such an escort."
Or Just Issue Radio Warnings
In any case, boarding the ship may not be required, Prest said, and that a radioed instruction to divert the ship to anchorage or to a harbor under escort may be sufficient.
But where they might go next is unclear.
"It is unlikely that Oman would want to be the repository for such vessels-that would put them in a very awkward position with their neighbors," said Prest, adding “the same is true for Pakistan."
It is also uncertain what happens even if a port were to be found. Might it mean the vessel and oil are seized as spoils of war, or impounded until the end of the war?
"These are questions I have not yet heard discussed or answered in the discourse," added Prest.
Shipping traffic data so far shows that some of the ships turned around have returned through the strait to the Persian Gulf.
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Strait of Hormuz traffic
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This story was originally published April 15, 2026 at 12:25 PM.